Real-time mass spectrometric investigation of the methanol oxidation in a direct methanol fuel cell

A mass spectrometric setup was designed which allows an on-line, and thus real-time, analysis of the products of methanol oxidation in a prototype direct methanol fuel cell (DMFC) operating at 150 to 190 C. Platinum-black and platinum-ruthenium were used as anode catalysts. The methanol/water mole ratio in the anode feed and the fuel cell operating temperature were varied, and the relative product distribution was determined as a function of these parameters. For pure methanol feed, methanaldimethylacetal was found to be the main product, while an excess of water in the anode under all conditions studied. Increase in the fuel-cell operating temperature led to an increase of the relative product distribution of CO{sub 2}. Platinum black was found to be more selective toward methylformate and methanaldimethylacetal formation than platinum-ruthenium. Cycling the fuel cell anode at 1 mV/s, platinum-ruthenium showed lower onset potentials for both CO{sub 2} ({approximately}0.2 vs. {approximately}0.35 V vs. RHE) and methanaldimethylacetal ({approximately}0.15 vs. {approximately}0.3 V vs. RHE) formation than platinum.